A cluster of powerful storms is set to disrupt Thanksgiving holiday travel for the Western US, with heavy snow cancelling flights in Denver and a higher risk of mudslides in parts of California. Winter storm warning and advisories cover the West from Oregon to Arizona and a flash flood watch stretches from north of Anaheim to the border with Mexico, the National Weather Service said. Parts of the Rockies were blanketed with more than a foot of snow, with blizzard-like conditions still bearing down. The arctic blast comes as millions of Americans plan travel for the Thanksgiving holiday on Thursday. “Travel will be very difficult to impossible, including Wednesday and Thanksgiving,’’ the weather service said.